


In Which Dipper’s Pet Demon Is A Pain In The Ass (Featuring the Armed Detective Agency)

by bakarasaka



Category: Gravity Falls, 文豪ストレイドッグス | Bungou Stray Dogs
Genre: Oneshot, another stupid crossover, idk where this came from
Language: English
Status: In-Progress
Published: 2019-12-27
Updated: 2019-12-27
Packaged: 2021-02-25 23:41:49
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,808
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21983848
Author URL: https://archiveofourown.org/users/bakarasaka/pseuds/bakarasaka
Summary: “The Armed Detective Agency, eh? Seems boring.” said Mason, learning against the wall with his eyes closed. “Why didn’t you name it something awesome like The Supernatural Investigation Squad? Or The Magical Mystery Solvers?”“Because this is reality and we’re not in some TV show.” Kunikida deadpanned.Mason cracked open an eye and looked at the blonde. “So you guys aren’t some rip-off Scooby Doo?”Yosano rubbed her temples. “For the last time, no one here gets your Western references!”Mason groaned, letting his eye fall back shut. “You guys are no fun. At least the guys in Tokyo appreciated my jokes.”
Relationships: Bill Cipher & Dipper Pines, Dipper Pines & Mabel Pines, Dipper Pines/Tanizaki Junichirou (Implied)
Comments: 2
Kudos: 31





	In Which Dipper’s Pet Demon Is A Pain In The Ass (Featuring the Armed Detective Agency)

“ Why did I decide to move to Yokohama, Japan again?” The thought was something Mason “Dipper” Pines spoke aloud as he ran away from the men dressed in black suits. 

** To get away from me, Dipshit.  **

Mason scowled as the demon inside his head spoke. But of course, he was right. 

** But that didn’t work real well, did it, Pinetree? **

“I swear to god, Bill. If you don’t shut up right now, I’m gonna make you regret it,” Mason grumbled. “Now can you please help me lose these guys!?”

** Oh, so  now  you want me help. What happened to shutting up? **

Mason rolled his eyes. “Just help me, Cipher!” He hissed. He could feel the dream demon going over the situation in his head, and tried to ignore him as his feet pounded the uneven pavement. 

** Fine, I’ll help you. But prepare to devour some chocolate when we get back.  **

Mason sighed, reaching up and touching the triangle seal he had on the base of his neck, and felt the familiar magic and strength rush through his body. He stopped running, relaxing his whole body and closed his eyes. The brunette’s senses intensified, and he heard the men stop running, and could smell the metal as they brought their guns out. 

The boy began to laugh as the bullets rained on him. There was a slight yellow tint around him, and as he opened his eyes, the men in suits felt fear. The boy’s eyes had gone yellow, with a black cat eye where the pupil should be. 

Mason Pines had become Bill Cipher. 

“Well, doesn’t this look like so much fun!” Bill said, laughing maniacally as the bullets continued to rain. 

_ Bill, don’t let those bullets hit me! _

Bill laughed. “Relax, Pinetree. Those metal pellets won’t hit you. It would be so boring if my favorite human died.”

That didn’t really ease Mason’s concern. 

Bill turned his attention back to the men in suits, and grinned devilishly. He lifted his arms up, and time slowed, the area around him and the men fading into black, grey and white. The yellow surrounding Bill became more pronounced, and the men felt a chill went down their spines as the demon lowered his head. 

Bill felt someone else enter his monochromatic realm, but let it slide as his grin widened from the feeling of fear coming from the men in suits. 

When the dream demon finally got bored of playing defense, he decided to go on offensive. He slowed down time even more, so that the bullets stopped mid-air, and picked off the men one by one by lifting a finger and throwing them in the air. 

When all of the men were unconscious, Bill reluctantly released his hold on Mason’s body and let the brunette have control again. 

Mason fell to his knees, the strength that Bill had brought with him had retreated, and he was back to his regular strength. He closed his eyes, and covered his ears, trying to get used to not being able to hear and see everything as well. Joining with Bill always was awesome, it was the aftermath that Mason hated. 

“Woah, are you okay?” Mason heard. He looked up to see a boy with blonde hair, overalls, and a straw hat standing over him. 

The American just coughed, smiled and nodded in response. “Yeah-“cough, cough. “-I’m fine.” Then his body decided to give out, and he collapsed on the ground. 

{•}

When Mason regained conscious, he let his eyes remain closed as he tried to remember what had happened. 

**Don’t you remember, Dipshit? You let me take control to get rid of those pansies in suits, and that weird kid picked you up.**

Mason sighed in his mind.  _Thanks for the recap, Bill._

** No problem, Pinetree .  **

“Kenji! How many times have I told you not to take in people from the street!” A male’s voice rang out. 

“...Eighteen...” The boy who Mason assumed was named Kenji replied. 

“Exactly! How many more times do I have to tell you for you to finally get it into your head!” The first voice yelled. 

“Uh, guys. I think he’s waking up,” another boy’s voice said. 

Mason groaned, and his eyes flutter open. He was laying on a desk with a strange group of people surrounding him. Including a familiar boy with blonde hair. He felt his anxiety skyrocket, but he tried to swallowed it down. 

Mason shot up, quickly touching near the base of his neck, beside where his triangle seal was. 

“Woah, woah, woah.” A man with a weird cape thing said, his hands out and eyes squinted. “Buddy, you’re safe!”

Mason scowled at the man, slowly taking his hand from the seal on his neck and crossing his arms. “Then why the hell did that blonde kid kidnap me!?” He spat in English. 

The male with a weird ponytail sighed, his own arms crossed, and leaned against the desks. “It’s a long story.” The voice spoke in English as well, and Mason recognized it as the first voice, the one yelling at ‘Kenji’. 

The boy in question, jumped up in front of the American. “Hallo! My name’s Kenji! What’s your name!?”

Mason stumbled back and his eyes widened with how bright the kid was. He was like a blonde Mabel. “...Mason...” He responded slowly. 

The blonde’s eye’s widened. “You’re foreign!? That’s so cool! This city really has everything!”

Mason backed away from ‘Kenji’ and accidentally backed into someone. He quickly turned around and gasped when he saw a women with a butterfly clip who looked impatient. “S-sorry!” He stammered, quickly backing away from her as well. 

The brunette finally backed into a wall and fell down into a sitting position. He went to rub his neck, and accidentally pressed on the triangle seal. 

Damnit. Mason thought as the world went black. Why do I keep doing that?

When Bill gained control, the people went on offense, pulling out weapons and stood facing the American. Bill opened his eyes and grinned wildly at the people standing in front of him. 

“Sup people. I’m Bill Cipher, Dipper’s pet demon,” the brunette said. “Anyone got any chocolate?”

Everyone looked over to the guy with squinted eyes, who’s eyes widened comedically. “Ah, why does it always have to be my snack rations being taken!”

So Bill got his chocolate and the people reluctantly introduced themselves. 

“Who’s Dipper?” Tanizaki, who was staring at the boy, asked. 

“Well, I guess he introduced himself as Mason. He doesn’t really go by Dipper anymore.” said Bill, his mouth filled almost completely with chocolate. 

Kunikida scoffed, and crossed his arms. “Why the hell would he go by ‘Dipper’ of all names.”

Bill took another bite of the chocolate bar, lifted his bangs to reveal Mason’s birthmark, then took another bite of his chocolate. 

“Oh so that’s why!” Kenji exclaimed. 

Bill devoured the rest of the chocolate bar, with the candy smeared around his mouth, making Kunikida cringe. “So this is the famous Armed Detective Agency. I’ve heard much about you.”

The women with a butterfly clip, Yosano, just hummed at that, while Ranpo exchanged a glance with her. 

Kenji leaned forward, eyes wide and sparkling. “Mr. Demon! What kinda things have you heard about us!?”

Bill chuckled. This kid was a riot. “Just about how odd it is that Yokohama has so many gifted in one place. The fact that none of you have killed the others off is fantastic! More soap operas for the omnipotent beings of the multiverse!”

Kunikida pushes his glasses up with an unamused look. “So, ah, Cipher. Where do you and Mason come from? And how do you speak such fluent Japanese?”

Bill waved a hand, swiping another bar of chocolate from Ranpo’s desk. “Dipshit here is from the States. California to be exact. And did you already forget?” Bill smirked devilishly and tapped his head. “I’m a demon. I’m fluent in every language ever.” He added in a stage whisper. 

“Does that mean you understand languages not from Earth?” asked Naomi, who was gripping onto her brother’s arm. 

Bill laughed her again. “Yes ma’am I do! I can also see you have some kinda trust issues by the way you’re holding onto your brother.” When Naomi gripped tighter to Tanizaki, the dream demon laughed again, for she had proven his point. 

“If you really are a demon,” Ranpo began with squinted eyes. “then how did Mason summon you?”

Bill‘s smirk shifted to a grin before answering. “It wasn’t Pinetree that summoned me, it was his great uncle, and then his arch nemesis. He just got the fortunate title of being my favorite human!”

_ Yeah, fortunate. Bill...what’s going on? _

** Ah, speak of the devil! **

_ Bill, seriously, what happened? _

** After you gave me control, thanks by the way, the humans introduced themselves, and are now in the middle of interrogating me.  **

_ Can you let me have control again?  _

** Ah, but things were just getting fun, Pinetree! **

_ Bill .  _

** Oh fine, you win.  **

The Armed Detective Agency tensed when the yellow haze around the possessed boy disappeared, and his eyes went back to their normal brown. 

Mason looked up, smiling wearily, placing down the bar of chocolate and wiping any off his face. “Hello, members of the ADA. I apologize for you having to meet my personal pain in the ass before me. Do any of you have a pen that I could borrow?”

Tanizaki jumped at the request and raced to his desk to grab a pen for the brunette. He tripped over his sister, who yelped, andshakily handed the pen to Mason. 

“Thank you, ah...” 

“T-Tanizaki.”

“Thank you, Tanizaki.” said Mason, smiling at the redhead. The brunette uncapped the pen, looking down and drawing the Bill zodiac on his arm with the summoning chant around it. 

The members of the agency just watched as the strange American wrote stuff on his arm. 

“Umm, what’s he doing?” Naomi whispered to Yosano. 

“I think he’s drawing a summoning circle.” The doctor replied. 

Mason glanced up before continuing his drawing. “To answer your question, I’m making it so Bill can’t eavesdrop on this conversation. He has a habit of doing that and selling information for entertainment.”

Kunikida looked outraged. “He violates people’s privacy like that! What a-“

“I know.” Mason sighed, placing the pen down. “I’ve lived with it since I was fifteen. Not really the best thing to have your demon blackmail you. Anyways, we should be safe now. You didn’t tell him anything to valuable, right?”

The agency members shook their heads, and Mason smiled. “Then we’re golden. Now, can you introduce yourselves to me again. Bill’s being an ass.”

{•}

“The Armed Detective Agency, eh? Seems boring.” said Mason, learning against the wall with his eyes closed. “Why didn’t you name it something awesome like The Supernatural Investigation Squad? Or The Magical Mystery Solvers?”

“Because this is reality and we’re not in some TV show.” Kunikida deadpanned. 

Mason cracked open an eye and looked at the blonde. “So you guys aren’t some rip-off Scooby Doo?”

Yosano rubbed her temples. “For the last time, no one here gets your Western references!”

Mason groaned, letting his eye fall back shut. “You guys are no fun. At least the guys in Tokyo appreciated my jokes.”

“It’s not that we don’t, ah, appreciate them. We just don’t, um, get them.” said Tanizaki, stumbling over his words in front of the brunette. 

Mason leaned in towards the redhead and smiled lazily. “Thank you yet again, Tanizaki.”

The ability user flushed.  He’s super close... He was almost disappointed when the brunette leaned away, jumping. 

Mason pulled out his phone. It was vibrating like crazy and the picture showed what looked like a female Mason, dressed in a purple sweater, grinning like crazy. The American winced as he took the call. 

“Hey, Mabel.” He said, tensed up. 

“ DIPPER! How’s Japan? Is it all you thought it would be? Have you met anyone yet? Has Bill caused any trouble yet? Did you meet some anime characters! Or even better, J-pop bands!”

The members of the Agency winced as they heard the loud, singsong voice from Mason’s cell. Mason’s face was stuck in a wince as he pointed to the phone and mouthed  “my sister”  to the Agency. 

“Ah, Japan’s good, people here are much more polite then in America.” Mason glanced at the ADA before turning his attention back to the phone. “Um, I’m with a group of people right now who are very welcoming. Bill didn’t necessarily start the trouble, but he fixed it. No and no.” 

“ Aw, to bad. Have you found yourself a job yet, bro-bro?”

Mason tensed, aware that he wasn’t the only one hearing his loud sister’s questions, and was all to aware of the eyes on him. 

“Uh, no not yet. No one seems to want to hire someone from America.” The brunette laughed awkwardly. “But I’m sure to find someone.”

Behind him, Yosano and Kunikida exchanged a glance before nodding. Ranpo noticed them, but didn’t say anything, because he figured what they had agreed upon.

“ That sucks. I hope you find somewhere. Oh! Grunkle Stan wanted me to tell you to find some hot old ladies for him, and Ford said to wish you luck with your studies .”

“Yep, that sounds like the old man.” snickered Mason. “Tell Stan to get off the couch to find someone himself, and Ford thank you.”

Mabel laughed through the phone. “ Yessiree! Love ya, bro-bro !”

“Love you too, Mabel.” The American ended the call and looked up to see a new face. “Uh, hello sir!”

The man was the President of the Agency, and the expression on his face was petrifying to say the least. 

**Way to not sound like a wuss, Pinetree.**

_ Shut the hell up, Bill.  _

** Yessiree, Boss! **

Mason tried keeping his face blank, but could tell that everyone in the room felt the anxious cloud built up around him. 

“Uhm, hello, sir?” It came out more as a question than expected, but at least the brunette managed to get some word out. 

“I heard that you were looking for a job,” The president, Fukuzawa, stated, cutting to the chase. 

Mason scratched the back of his neck, carefully in order to not touch the mark that summoned his demon. “Erm, yes, sir I am. No really wants to hire a foreigner who has just moved here though, so it is kind of difficult at the moment.”

Fukuzawa’s expression stayed stoic as ever. “What if I offered you a job here, as an intern of course. You don’t possess an ability, but your plus one could be useful in times of great need. Also from what Ranpo has told me, your intelligence and instinct seems perfect for an invigorator.”

Mason froze, staring at the man in front of him as if he was crazy. “Are you asking me... if I want to work here with all of you?”

The man nodded, face unchanged. “Only if you want to of course. No pressure.” 

Mason sweatdropped as he noticed the last part was added as an after thought. 

The brunette was well aware of the burning stares of everyone in the room as he thought his decision over. 

** Take it, Mason.  **

_...What did you say, Bill? _

** Take it you, dumbass. This has been your dream since you were like, what, ten? It’s a once in a lifetime opportunity, it seems to pay well, and it’s a free fucking job! **

_...Even though it exploits and could possible use your powers without full consent.  _

Mason could practically see Bill pinching the bridge of his nose as the eye roll and sigh was made known. 

** Kid, I’ve been used and exploited for millennia. I’m a demon, after all! But if you seriously think that this power is all mine, then your fucking delusional. We share this thing, if I like it or not. **

_...Thank you, Bill.  _

** Yeah, yeah, just speak up, Pinetree.  **

Mason lifted his head, unaware that it even fell in the first place, and met eyes with Fukuzawa. 

“I-I accept the offer. Thank you so much, and I hope to be of good help to the agency.” The brunette exclaimed, watching as the president’s facade cracked a bit to reveal a smile. 

“Yes! The American is working here!” Kenji yelled, jumping up and down and smiling brightly. 

Kunikida pushes up his glasses and smiled at the younger boy. “Welcome to the team, Mason.”

As everyone started to congratulate the brunette on joining the agency, the door flew open and everyone except Mason just sighed in response. Standing in the doorway was a brown haired man with a tan coat and bandages who looked triumphant. 

“Kunikida!~ I found a new suicide method, wanna help me out!~”

** What...what the actual fuck is wrong with him?! **


End file.
